Method and apparatus for positioning reinforcement bars in concrete pavements



Aug. 8, 1967 J. TAYLOR 3,334,559

METHOD AND APPARATUS FOR POSITIONING REINFORCEMENT BARS IN CONCRETE PAVEMENTS Filed June 9, 1965 2 Sheets-Sheet 1 I I I N 1 5 l i A l 4 J a 1 I f a INVENTOR /van .1 fay/or 2 Sheets-Sheet INVENTOR /v0n J. Taylor l. J. TAYLOR SITIONLNG REINFORCEMENT BARS IN CONCREIE PAVEMENTS Aug. 8, 1967 METHOD AND APPARATUS FOR PO Filed June 9, 1965 United States l atent O ice METHOD AND APPARATUS FOR POSITIONING REINFORCEMENT BARS IN CONCRETE PAVE- MENTS Ivan J. Taylor, Bethlehem, Pa. (809 S. Haswell Drive, Bryan, Tex. 77801) Filed June 9, 1965, Ser. No. 462,633 20 Claims. (Cl. 94-39) This invention relates to methods and apparatus for the positioning of steel reinforcing in concrete pavements. It relates particularly to methods and apparatus for placing individual steel reinforcing bars in continuously reinforced pavements.

Concrete pavements for highways and the like are usually constructed as a series of individual but interconnected reinforced concrete slabs separated from each other by expansion and contraction joints extending transversely to the centerline of the pavement every 30 to 100 feet along the length of the pavement.

It has long been known by highway engineers that the transverse joints require constant maintenance and are frequently the cause of pavement failure. The closely spaced transverse joints are also very annoying to the driver, especially in summer, when the expansion of the slabs causes the joint filler material to be extruded from the joints as a series of low but noticeable ridges extending across and above the surface of the pavement.

In recent years a new type of concrete pavement, known as continuously reinforced pavement, has been developed and is gradually replacing the more conventional type of pavement described above. In continuously reinforced pavements all the transverse joints are eliminated except for the transverse construction joints placed at the end of each day's paving operations and the transverse joints where the continuously reinforced pavement meets a fixed structure, such as a bridge.

As the name implies the steel in continuously reinforced pavement is placed so as to provide a reinforcement whose strength is continuous and unbroken by the heretofore required transverse expansion and contraction joints. The highway engineers who advocate continuously reinforced pavements know that cracks will occur in the pavement for various reasons regardless of the type of construction used. It is their contention that the mere existence of cracks in the pavement is not harmful but that the harmful effects of cracking occur only when the cracks are permitted to widen sufficiently to permit the intrusion of water and dirt or to permit the uneven distribution of wheel loads. In continuously reinforced pavements, the sides of the cracks that do occur are held tightly together by the continuous longitudinal steel reinforcement.

The reinforcing steel for continuously reinforced pavements has been the same as that used for conventional reinforced concrete pavements; namely, welded wire fabric, rectangular deformed bar mats and individual deformed bars. Many contractors have preferred to use Welded wire fabric and rectangular deformed bar mats for much of the continuously reinforced pavement built to date primarily because these two types of reinforcement require considerably less time and labor to install in the field than does the individual deformed bars. Although individual deformed reinforcing bars are cheaper to buy, easier to ship and easier to handle in the field than either welded wire fabric or deformed bar mats, it is the high cost of installation that has prevented a wider acceptance of this type of reinforcement for concrete pavements.

The few cases of pavement failure in the continuously reinforced pavements built to date has occurred primarily in the areas Where the longitudinal reinforcement is overlapped and spliced. This is thought by many engineers to 3,334,559 Patented Aug. 8, 1967 be the result of all the splices occurring in a line at right angles to the longitudinal centerline of the pavement. With welded wire fabric and deformed bar mats all the splices occur in a line at right angles to the longitudinal centerline of the pavement because of the rectangular shape of these reinforcing units. It has been proposed to stagger the splices in the longitudinal reinforcement so that they do not all occur in a straight line 'at right angles to the centerline of the pavement. However, staggered splices are only possible with individual reinforcing bars each of which has to be positioned and tied in place by hand. This a very time consuming operation which adds considerably to the construction costs for the pavement.

It has also been observed that the steel reinforcement placed in the pavement transverse to the longitudinal centerline of the pavement contributes very little to the overall strength of the pavement. Instead, the main function of the transverse reinforcing members, Welded to the longitudinal reinforcement in the case of welded wire fabric, and tied to the longitudinal members in the case of individual deformed bars and bar mats, is to hold the longitudinal reinforcing members in the proper spaced, parallel relationship during their placement and the pouring of the concrete. Considerable savings, both in money and material, could be achieved if individual longitudinal reinforcing bars could be accurately positoned in the concrete slab without the necessity of holding them in the proper spaced, parallel relationship using transverse tie members.

It is therefore an object of my invention to provide apparatus which will automatically position individual longitudinal reinforcing bars in concrete pavements.

It is another object of my invention to provide apparatus which eliminates the need for the large amount of hand labor heretofore required for the placement of individual longitudinal reinforcing bars in concrete pavements.

It is a further object of my invention to provide apparatus which automatically staggers the splices between successive lengths of individual longitudinal reinforcing bars so that the splices do not all occur in a straight line at right angles to the longitudinal centerline of the pavement.

It is a still further object of my invention to provide apparatus which permits individual longitudinal reinforcing bars to be positioned in the concrete with any desired spacing between adjacent bars and any desired amount of and overlap between successive bars.

It is another object of my invention to provide an improved method of constructing a reinforced concrete pavement using individual longitudinal reinforcing bars as the reinforcement.

It is still another object of my invention to provide an improved form of reinforced concrete pavement having individual longitudinal reinforcing bars as the reinforcement.

I have discovered the foregoing objects can all be obtained by using apparatus comprising a frame adapted to move along and above the subgrade in a longitudinal direction, a set of driven endless chain conveyors mounted on the frame to convey individual reinforcing bars across and under the frame in a transverse direction to a predetermined position between spaced parallel forms, and a second set of driven endless chains parallel to the first set of endless chains and adapted to separate each of the bars one at a time from the first set of driven endless chains Whenever each of the bars is in its predetermined position.

Referring to the drawings which illusrtate an embodiment of my invention.

FIGURE 1 is a broken top according to this invention.

FIGURE 2 is a section taken along line 2-2 of FIG- plan View of apparatus URE 1, but with various portions of the drive mechanism of the apparatus omitted for purposes of clarity.

FIGURE 3 is a plan view of a portion of the reinforced concrete pavement of my invention.

FIGURE 4 is a section taken along line 44 of FIG- URE 1.

Referring to FIGURES 1 and 2, the numerals 1 and 1 indicate a pair of spaced parallel metal forms which not only define the sides of the concrete pavement but also serve as tracks supporting the apparatus of my invention. This apparatus, according to one embodiment of my invention comprises a rectangular metal frame 2 having a pair of parallel side members 3 and a pair of parallel end members 4 all joined together. A pair of flanged traction wheels 5 are secured to the ends of a drive shaft 6 suitably journaled in the parallel side members 3 near one end of the frame 2. A second pair of flanged wheels 7 are secured to the ends of shaft 8 journaled in the parallel side members 3 near the other end of frame 2. Flanged wheels 5 and 6 are suitably spaced and adapted to travel on the top surfaces of spaced parallel metal forms 1 and 1'.

An internal combustion engine or other form of prime mover is mounted on frame 2 near drive shaft 6. Engine 20 drives shaft 9 through a suitable gear box 10. Sprocket 11 is attached to shaft 9 and drives endless chain 12 and sprocket 13 attached near the middle of shaft 14. A pair of bevel gears '15 and 16 are attached to opposite ends of shaft 14. A clutch assembly 17 mounted on drive shaft 6 and comprising a pair of opposed bevel gears 13 which can be selectively engaged with bevel gear 15 by selector handle 19 permits flanged traction wheels 5 to be driven forward, backward or not at all along spaced parallel metal forms 1 and 1'.

Bevel gear 16 engages bevel gear 19 attached to shaft 21 journaled in parallel side members 3 in a position parallel to but between drive shaft 6 and shaft 8. Bevel gears 22 and 23 attached to opposite ends of shaft 21 engage bevel gears 24 and 25 respectively, which are attached to parallel shafts 26 and 27 positioned along side and parallel to side members 3 of frame 2. Bevel gears 22, 23, 24 and 25 are arranged as shown in FIGURE 1 so that parallel shafts 26 and 27 rotate in the same direction. In addition, bevel gears 24 and 25 are sized so that shaft 27 is rotated at a speed at least twice that of shaft 26. It will be understood that all rotating shafts in this apparatus will be journaled in the side members 3 of frame 2 or attached to the frame by pillow block bearings 28 or the like.

Positioned along shaft 26 are two sprockets 30 that are attached to and rotate with shaft 26 and two sprockets 31 that are free to rotate independent of shaft 26. Positioned along shaft 27 are two sprockets 32 that are attached to and rotate with shaft 27 and two sprockets 33 that are free to rotate independent of shaft 27. Sprockets 30, 31, 32 and 33 are all approximately the same diameter.

A set of parallel endless chains 34 engage sprockets 30 and 33 while a second set of parallel endless chains 35 engage sprockets 31 and 32. Both sets of endless chains surround frame 2. While I have illustrated two endless chains comprising one set, it will be apparent that more than two parallel endless chains may be used in a set with a corresponding increase in the number of sprockets on shafts 26 and 27.

It will also be apparent that the set of endless chains indicated by the numeral 35 will be driven in the same direction (illustrated by arrows) but at a speed at least twice the speed of the set of endless chains indicated by the numeral 34.

As best shown in FIGURE 2, endless chains 35 are each provided with a series of hook-like links 36 spaced at regular intervals along a length of chain 35 substantially equal to the width of the pavement, i.e. the distance between the spaced parallel metal forms 1 and 1', and

with the hook opening facing away from the direction of movement of chains 35. Endless chains 34 are each provided with a pair of projecting links 37 spaced from each other by a distance substantially equal to half the length of the chain 34. The purpose and function of hook-like links 36 and projecting links 37 will be explained later.

Support members 38 consisting of a pair of angle bars with one leg upstanding are positioned across frame 2 adjacent to and parallel to endless chains 35 with the top edges of the upstanding legs slightly above the top surface of endless chains 35. Support members 38 are extended beyond slide member 3 at one side of frame 2 to provide a storage platform 39 for individual longitudinal reinforcing bars 40.

In constructing pavements using the apparatus and methods of my invention, spaced parallel metal forms 1 and 1' are first aligned and secured to the subgrade of the roadway. Paving apparatus (not shown) traveling on the top surface of forms 1 and 1' deposits a layer of concrete approximately equal to half the thickness of the finished pavement on the subgrade between forms -1 and 1'. Thereafter the apparatus of my invention, traveling on the top surfaces of forms 1 and 1', positions individual longitudinal reinforcing bars 40 on the surface of the layer of fresh concrete as shown in FIGURE 2. Additional paving apparatus then deposits a second layer of concrete approximately equal to half the thickness of the finished pavement on top of the first layer of concrete and the reinforcing bars and also strikes off the concrete level with the top surfaces of forms '1 and 1'.

Alternatively, the full thickness of the pavement may be poured at one time in which case the apparatus of my invention immediately follows the paving apparatus and positions the individual longitudinal reinforcing bars 40 on the surface of the fresh concrete. Immediately following the apparatus of :my invention is apparatus (not shown) which vibrates the fresh concrete and, with proper control, will cause the individual longitudinal reinforcing bars 40 to sink vertically into the concrete to a position approximately half the thickness of the finished pavement.

The particular practice chosen will depend on the equipment the contractor has at its disposal and the pavement specifications.

In operating the apparatus of my invention, bundles of indiv1dual straight reinforcing bars 40 cut to the proper length are deposited on platform 39. Individual reinforcing bars 40 are then placed on support members 38 and across endless chains 34 and 35 so that each bar is between a pair of the spaced hook-like links 36 of endless chains 35 as shown in FIGURE 1. As chains 35 move in the direction shown by the arrows in FIGURES 1 and 2, the back side of a hook like link 36 on each of chains '35 will engage reinforcing bar 4-0 and slide or roll bar 40 along support members 38 in the direction indicated by the arrows in FIGURE 1. Since the top surfaces of support members 38 are slightly above the top surfaces of endless chains 35 and 36, most of the weight of the reinforcing bars 40 will be supported by the support bars 38 and not by the chains.

At the point where the endless chains 35 go around sprockets 32, the reinforcing bar 40 will no longer be pushed by hook-like links 36, but will fall under its own weight and be caught in the hooks of the preceding pair of hook-like links 36 as shown in FIGURE 2. The reinforcing bar 40 is then transported by the hook-like links 36 to a predetermined position beneath frame 2 and betWZCIII and parallel to the spaced parallel metal forms 1 an At this point, the reinforcing bar 40 is dislodged and separated from the hook-like links 36 by a pair of projecting links 37 mounted on chains 34 which travel in the same direction but at a much slower speed than chains 35. This is most clearly shown in FIGURE 2. The bar falls under its own weight onto the surface of the layer of fresh concrete below.

In this manner, a continuous series of longitudinal reinforcing bars 40 are deposited one at a time in substan- .tially uniform spaced parallel relationship to eachother across the full width of the concrete pavement between forms 1 and 1' and beneath frame 2.

While endless chains '34 and 35 are depositing the reinforcing bars 40 in the fresh concrete, traction wheels 5 have been propelling frame 2 forward at a predetermined speed along the top surfaces of forms '1 and 1' in a longitudinal direction parallel to said forms. The forward movement of frame 2 causes each of the reinforcing bars 40 to be deposited on the fresh concrete with the ends of the bar slightly ahead of the respective ends of the bar laid just previously as shown in FIGURES 1 and 3.

Since hook-like links 36 are spaced along only a portion of the length of endless chains 36 substantially equal to the width of the pavement, the individual reinforcing bars 40 will 'be deposited on the fresh concrete one at a time, from right to left in FIGURE 1 until the last bar adjacent to form 1' has been deposited. During this time the apparatus will have continued to move forward along forms 1 and 1' at a constant speed a distance substantially equal to the length of reinforcing bar 40 deposited on the concrete adjacent to form 1. The transversely moving chains 34 and 35, having received a new supply of individual reinforcing bars 40 from the platform 39, will once again begin depositing these bars one at a time from right to left in FIGURE 1 on the fresh concrete between forms 1 and 1' and overlapping the ends of the series of bars laid just previously.

This method of placing the reinforcing bars results in a continuous arrangement of ovenlapped series of spaced parallel longitudinal reinforcing bars similar to that shown in FIGURE 3. As illustrated by FIGURE 3, lines adjoining the respective ends of each of the spaced parallel longitudinal reinforcing bars 40 in a series across the width of the pavement will be oblique to the longitudinal axes of the bars 40 and forms 1 and 1'. Furthermore, as illustrated by FIGURE 3, the ends of the bars 40 in one series will overlap the ends of the bars in the preceding or succeeding series of bars by a predetermined substantially equal amount.

The amount of such end overap is controlled by the speed of the endless chains 34 and 35 in relation to the forward speed of the apparatus along forms 1 and 1. The oblique angle between forms 1 and 1 and the straight lines joining the respective ends of the individual longitudinal reinforcing bars across the width of the pavement is governed by the pavement width, the bar length and the desired amount of end overlap and is expressed by the following formula:

tangent A W/L0 Where A is the oblique angle between forms 1 and 1' and the straight lines joining the respective ends of the longitudinal bars in a series across the width of the pavement.

W is the distance between forms 1 and 1'.

L is the length of the bars.

0 is the amount of end overlap between successive series of bars.

The spacing between individual parallel longitudinal bars is controlled by the spacing between the hook-like links 36 on endless chains 35.

As an example, apparatus of my invention designed to position bars 20 feet long with a one foot end overlap and to travel on forms 1 and 1' spaced 24 feet apart, will position the bars so that the ends of the bars fall on a straight line at an angle of approximately 51 to the longitudinal axes of the bars and to forms 1 and 1'. A typical spacing between parallel bars for such an arrangement might be 6 inches.

Since most highways within a state are built to stand- 6 ard specifications, changes in the gearing of the apparatus or the spacing of the hook-like links will not normally be necessary.

I have also discovered that I am able to construct a rectangular reinforced concrete pavement superior to previous concrete pavements While using considerably less reinforcing steel by using a steel reinforcing which consists solely of a plurality of spaced, individual unconnected parallel steel bars whose longitudinal axes extend in the direction of the length of the pavement. The ends of the bars are arranged to fall substantially on parallel straight lines oblique to the longitudinal axes of the bars and to overlap the ends of additional bars similarly arranged in the pavement by a uniform amount.

In the pavement I have just described, there are no transverse reinforcing or steel tie members extending across the individual longitudinal reinforcing bars. However, in order to meet certain pavement specifications when using the apparatus and methods of my invention, it may be necessary to place across individual transverse reinforcing bars across the longitudinal bars. This may be done most conveniently by hand after the individual longitudinal bars have been positioned in the concrete according to the methods of my invention.

While I have described the apparatus of my invention being used with conventional paving equipment which travels on the top surfaces of fixed side forms fastened to the subgrade, it would be possible to incorporate my apparatus for positioning reinforcing bars in the recently developed slip-form pavers. The slip-form paver travels directly on the prepared su'bgrade and is essentially a single machine that spreads, tamps, vibrates and finishes the concrete in a single pass operation and, in addition, hauls its own side forms from which a ribbon of concrete is extruded.

As many possible embodiments may be made of my invention without departing from the scope thereof, it is to be understood that all matter set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. Apparatus for inforcing bars in a grade between a comprising:

(a) a wheel-supported frame adapted to travel on the top surfaces of said forms,

(b) means to propel said frame along said forms in a longitudinal direction parallel to said forms,

(0) conveying means mounted on said frame for receiving individual reinforcing bars and transporting each of said bars in a direction transverse to the direction of movement of said frame to a predetermined position beneath said frame and between and parallel to said forms, and

(d) means to separate each of said bars one at a time from said conveying means whenever each of said bars is in said predetermined position.

2. Apparatus for positioning individual longitudinal reinforcing bars in a concrete pavement poured on a subgrade between a pair of spaced parallel metal forms comprising:

(a) a wheel supported frame adapted to travel on the top surfaces of said forms,

(b) means to propel said frame along said forms in a longitudinal direction parallel to said for-Ins,

(c) a first set of driven endless chains mounted on said frame and surrounding said frame and adapted for receiving spaced individual reinforcing bars and transporting each of said bars in a direction trans- Verse to the direction of movement of said frame to a predetermined position beneath said frame and between and parallel to said forms, and

(d) a second set of driven endless chains mounted on said frame and surrounding said frame parallel positioning individual longitudinal reconorete pavement poured on a subpair of spaced parallel metal forms to said first set of endless chains and adapted to separate each of said bars one at a time from said first set of driven endless chains whenever each of said bars is in said predetermined position.

3. Apparatus according to claim 2 wherein the first set of endless chains and the second set of endless chains are driven in the same direction but at different speeds.

4. Apparatus according to claim 2 wherein the first set of endless chains is driven at a speed at least twice the speed of the second set of endless chains.

5. Apparatus according to claim 2 wherein the frame, the first set of endless chains and the second set of endless chains are all driven by a common drive means.

6. Apparatus for positioning individual longitudinal reinforcing bars in a concrete pavement poured on a subgrade between a pair of spaced parallel metal forms comprising:

(a) a wheel supported frame adapted to travel on the top surface of said forms,

(b) means to propel said frame along said forms in a longitudinal direction parallel to said forms,

(c) a first set of driven endless chains mounted on said frame and surrounding said frame and adapted to move in a direction transverse to the direction of movement of said frame,

((1) a plurality of spaced hook-like links mounted in each of the chains comprising said first set of chains and adapted for receiving and transporting individual reinforcing bars to a predetermined position beneath said frame and between and parallel to said forms,

(e) a second set of driven endless chains mounted on said frame and surrounding said frame adjacent to said first set of chains and adapted to move in the same direction as said first set of chains,

(f) a pair of projecting links mounted in each of the chains comprising said second set of chains and adapted to separate each of said bars one at a time from said hook-like links whenever each of said bars is in said predetermined position.

7. The apparatus of claim 6 wherein the hook-like links are spaced only along a portion of each of said first set of driven endless chains that is substantially equal to the distance between said forms.

8. The apparatus of claim 6 wherein the projecting links in each of the chains comprising the second set of chains are spaced from each other by a distance substantially equal to one half the length of said chain.

9. A method of constructing a continuously reinforced concrete pavement on a subgrade between a pair of spaced parallel forms that define the sides of the pavement comprising:

(a) depositing a layer of fresh concrete on said subgrade between said forms,

(b) beginning adjacent to one of said forms, placing one at a time, a group of individual unconnected reinforcing bars on the surface of said layer of concrete in a substantially uniform spaced parallel relationship to each other and with the longitudinal axes of said bars parallel to said forms,

(c) positioning the respective ends of said bars so that said ends fall substantially on a pair of parallel lines oblique to the longitudinal axes of said bars,

((1) repeating steps (b) and (c) with additional groups of bars, the ends of the bars in each group overlapping the ends of the bars in each adjacent group,

(e) depositing a second layer of fresh concrete on the first layer of fresh concrete and on said groups of bars.

10. The method of claim 9 wherein the thickness of each of the layers of fresh concrete are substantially equal to one half the thickness of the pavement.

11. A method of constructing a continuously reinforced concrete pavement on a subgrade between a pair of spaced parallel forms that define the sides of the pavement comprising:

(a) depositing a layer of fresh concrete on said subgrade between said forms,

(b) beginning adjacent to one of said forms, placing one at a time, a group of individual unconnected reinforcing bars on the surface of said layer of concrete in a substantially uniform spaced parallel relationship to each other and with the longitudinal axes of said bars parallel to said forms,

(c) positioning the respective ends of said bars so that said ends' fall substantially on a pair of arallel lines oblique to the longitudinal axes of said bars,

((1) repeating steps (-b) and (c) with additional groups of bars, the ends of the bars in each group overlapping the ends of the bars in each adjacent group,

(e) vibrating said layer of concrete and said groups of bars to further position said bars substantially midway between the top and bottom surfaces of said layer of concrete.

12. A rectangular continuously reinforced concrete pavement of relatively great length compared to its width and thickness, the reinforcing consisting solely of longitudinal steel rod-like members extending along the full length of said pavement and integrally bonded to the concrete, said members arranged in successive groups, each of said groups comprising a plurality of spaced individual unconnected parallel steel bars whose longitudinal axes extend in the direction of the length of said pavement, the respective ends of all of said bars in each group falling substantially on a pair of parallel straight lines oblique to the longitudinal axes of said bars.

13. A rectangular continuously reinforced concrete pavement of relatively great length compared to its width and thickness, the reinforcing consisting solely of longitudinal steel rod-like members extending along the full length of said pavement and integrally bonded to the concrete and positioned substantially midway between the top and bottom surfaces of said pavement, said members arranged in successive groups, each of said groups comprising a plurality of spaced individual unconnected parallel steel bars, the longitudinal axes of said bars extending in the direction of the length of said pavement and the respective ends of all of said bars in each group falling substantially on a pair of parallel straight lines oblique to the longitudinal axes of said bars.

14. A rectangular continuously reinforced concrete pavement of relatively great length compared to its width and thickness, the reinforcing consisting solely of longitudinal steel rod-like members extending along the full length of said pavement and integrally bonded to the concrete, said members arranged in successive groups, each of said groups comprising a plurality of spaced individual unconnected parallel steel bars whose longitudinal axes extend in the direction of the length of said pavement, the respective ends of said bars in each group falling substantially on a pair of parallel straight lines oblique to the longitudinal axes of said bars and overlapping the ends of bars similarly arranged in the next group.

15. Apparatus for positioning individual longitudinal reinforcing bars in a concrete pavement poured on a subgrade between .a pair of spaced parallel metal forms comprising:

(a) a frame supported above said subgrade,

(b) means to propel said frame in a longitudinal direction along said subgrade,

(c) conveying means mounted on said frame for receiving individual reinforcing bars and transport ing each of said bars in a direction transverse to the direction of movement of said frame to a predetermined position beneath said frame and between and parallel to said forms, and

(d) means to separate each of said bars one at a time from said conveying means whenever each of said bars is in said predetermined position.

16. The apparatus according to claim 15 wherein the spaced parallel metal forms move in a longitudinal direction.

17. Apparatus for positioning individual longitudinal reinforcing bars in a concrete pavement poured on a subgrade between a pair of spaced parallel metal forms comprising:

(a) a frame supported above said subgrade,

(b) means to propel said frame in a longitudinal direction along said subgrade,

(c) a first set of driven endless chains mounted on said frame and surrounding said frame and adapted for receiving spaced individual reinforcing bars and transporting each of said bars in a direction transverse to the direction of movement of said frame to a predetermined position beneath said frame and between and parallel to said forms, and

(d) a second set of driven endless chains mounted on said frame and surrounding said frame parallel to said first set of endless chains projecting links mounted in said second set of chains adapted to engage and separate each of said bars one at a time from said first set of driven endless chains whenever each of said bars is in said predetermined position.

18. Apparatus according to claim 17 wherein the first set of endless chains and the second set of endless chains are driven in the same direction but at different speeds.

19. Apparatus according to claim 17 wherein the first set of endless chains is driven at a speed at least twice the speed of the second set of endless chains.

20. Apparatus according to claim 17 wherein the frame, the first set of endless chains and the second set of endless chains are all driven by a common drive means.

References Cited UNITED STATES PATENTS 1,279,431 9/1918 Poulston 94-18 1,424,169 8/1922 Koehring 94-39 1,546,107 7/1925 Robb 94-39 1,996,153 4/1935 Heltzel 94-39 2,077,356 4/1937 Day 94-39 2,389,773 11/ 1945 Golden 94-39 2,950,659 8/1960 Smiley 94-39 3,083,621 4/1963 Woolley et a1 94-39 JACOB L. NACKENOFF, Primary Examiner. 

1. APPARATUS FOR POSITIONING INDIVIDUAL LONGITUDINAL REINFORCING BARS IN A CONCRETE PAVEMENT POURED ON A SUBGRADE BETWEEN A PAIR OF SPACED PARALLEL METAL FORMS COMPRISING: (A) A WHEEL-SUPPORTED FRAME ADAPTED TO TRAVEL ON THE TOP SURFACES OF SAID FORMS, (B) MEANS FO PROPEL SAID FRAME ALONG SAID FORMS IN A LONGITUDINAL DIRECTION PARALLEL TO SAID FORMS, (C) CONVEYING MEANS MOUNTED ON SAID FRAME FOR RECEIVING INDIVIDUAL REINFORCING BARS AND TRANSPORTING EACH OF SAID BARS IN A DIRECTION TRANSVERSE TO THE DIRECTION OF MOVEMENT OF SAID FRAME TO A PREDETERMINED POSITION BENEATH SAID FRAME AND BETWEEN AND PARALLEL TO SAID FORMS, AND (D) MEANS TO SEPARATE EACH OF SAID BARS ONE AT A TIME FROM SAID CONVEYING MEANS WHENEVER EACH OF SAID BARS IS IN SAID PREDETERMINED POSITION. 